South African police insisted Friday they only fired in self-defence in a clash with striking mineworkers in which 34 people died, the deadliest protest since the end of apartheid.As images of the gunfire cycled endlessly on television, police chief Riah Phiyega told a news conference that officers only used live ammunition after negotiations and crowd control tactics had failed."The militant group stormed toward the police, firing shots and wielding dangerous weapons,” she said."Police retreated systematically and were forced to utilise maximum force to defend themselves. The total death (toll) of the protesters currently stands at 34 with more than 78 injured.”So far 259 people had been arrested on various charges stemming from the clash Thursday at the platinum mine run by London-listed Lonmin, she added.The workers at the Marikana mine were on a weeklong wildcat strike demanding a tripling of their wages from the current 4,000 rand ($486, 400 euros) a month.A union leader compared Thursday’s shooting to the notorious Sharpeville massacre of 1960, in the darkest days of the apartheid era, when police killed 69 black protestors.It was the deadliest police action in South Africa since 1985, when more than 20 blacks were shot dead by apartheid police in Cape Town as they marked the 25th anniversary of Sharpeville.This time the gunfire came from a mostly black police force, shooting at poor black miners whose living conditions have hardly improved in the 18 years since apartheid yielded to all-race democracy."I always thought that the Sharpeville massacre was history and it would never happen again. What we experienced yesterday under the democratic government was similar to Sharpeville,” said Joseph Mathunjwa, head of the Association of Mineworkers and Construction Union (AMCU).Before Thursday, 10 people had already died at Marikana in attacks blamed on rivalry between the radical new AMCU and the powerful National Union of Mineworkers, a major ally of the ruling African National Congress.The two unions have condemned that violence, denied taking part in the killings, and blamed each other for the troubles.As the death toll mounted Friday, President Jacob Zuma cut short a visit to neighbouring Mozambique for a regional summit and flew to Rustenburg, the town nearest the mine.His handling of the unrest could prove pivotal as he tries to tamp out challenges within the ANC to his leadership, ahead of the elective conference in December where he will seek a second term as party boss.The NUM is one of South Africa’s most powerful unions, having produced several top ANC leaders, including Deputy President Kgalema Motlanthe -- seen as a potential challenger to Zuma.The violence points "to a heated political atmosphere in South Africa that is playing itself out on the ground within the unions,” labour analyst Daniel Silke said.Tensions are particularly high among platinum mine workers, who have watched as several mines shut down this year with companies battling to cope with low prices for the metal, he said.But for many South Africans, the crucial question will be the police handling of the strike, which they approached in bulletproof vests but without other protective gear, like riot shields."It comes down to inadequate training, to too few police dealing with too many people, without adequate protection like shields,” said Lucy Holborn, research manager at the South African Institute of Race Relations."In a crowd control situation, police shouldn’t be armed with liveammunition,” she said.